Quick-hardening silicone materials with good adhesive properties

ABSTRACT

The present invention relates to mixtures containing bi-functionally terminated diorganopoly siloxanes aminosilane or oxime or alkoxy crosslinking agents, and optionally, filling materials, suitable additives, pigments, colorants, anti-oxidation pigments, anti-heat pigments, and light-protection pigments in addition to solvents and plasticizers. Said mixtures contain water and a catalyst in the form of an acidic or basic neutral salt as an accelerating cross-linking agent.

The present invention concerns a kit for the production of mixtures ofat least bifunctionally terminated diorganopolysiloxanes, amino silanecross-linking agents, as well as possibly filling materials, suitableadditives, pigments, colouring materials, oxidation- heat- andlight-protesting pigments, as well as solvents and plasticisers.

Such organopolysiloxane mixtures, also known as cold-vulcanising,monocomponent silicone rubbers, usually cross-link at room temperaturewith take up of water from the surrounding atmosphere to give rubberelastic polymers. As chain lengtheners and cross-linkers, there are usedbi- and preferably higher functional aminosilane compounds which, byreaction with the polysiloxane or by hydrolysis, split off amines andthus initiate the formation of a macromolecular meshwork. Afterhardening has taken place, such masses are characterised by a goodinherent adhesion to the most varied material surfaces and by aGenerally high stability towards the action of temperature, light,moisture, as well as chemicals.

The hardening of such monocomponent polysiloxane mixtures cross-linkingat room temperature with the take up of moisture takes placecomparatively slowly since the water necessary for the reaction mustdiffuse from the surrounding atmosphere into the interior of the mass,Therefore, the speed of the hardening through decreases with progressivereaction in the interior of the mass. In the case of low atmosphericmoisture or in the case of an unfavourable ratio of surface to volume ofthe silicone mass, the reaction can be very slow or, in the case ofvapour-tight closed spaces, come to a complete stop.

The per se multiple possibilities of use of such atmosphericmoisture-hardening silicones as sealing or adhesive material are,especially in the case of use in industrial fabrication, limited becauseof the slow hardening. Admittedly, silicone rubber systems hardeningquickly at room temperature or also first at elevated temperature areknown but their use fails frequently by the deficient inherent adhesionor also the comparatively low temperature stability of these products.However, if one uses silicones hardening only slowly under the influenceof atmospheric moisture, in the case of short cycle times desired foreconomic reasons large intermediate storage for sealed off or adheredparts are necessary in order to ensure the hardening. This intermediatestorage must possibly be additionally climatised or moistened. Undercertain circumstances, in this way already large numbers of pieces areproduced before a testing for fault-freedom and function of the producedgoods is first possible. Large-surface adhesions between diffusion-tightsurfaces can, in practice, be carried out just as little withatmospheric moisture-hardening silicones as the production of formedbodies in closed moulds.

If one adds water in liquid form to the known amino-silane-containingand atmospheric moisture-hardening masses, in comparison to thecross-linking with atmospheric moisture, a certain acceleration of thehardening is achieved. However, this form of the cross-linking does notlead to end products with material properties such as are obtained inthe case of purely atmospheric moisture cross-linking. On the contrary,masses result which over time remain substantially softer, display poorinherent adhesion and remain still a very long time swollen with theamine resulting as cross-linking fission product. Correspondingly, theamine smell, usually found to be extremely unpleasant, also persists fora long time.

From DE 4431489 it is known that aminosilane-cross-linking siliconemasses harden rapidly when one adds to the system a paste which containswater and an inorganic or organic compound which reacts with the amineswith salt formation. Inorganic and organic acids come into considerationas such compounds. The addition of these accelerating substances takesplace immediately before the working up of the mass. The acid reactswith the fission product, the amine, with salt formation, whereby thereaction equilibrium is displaced to the side of the product. The saltformed remains in the polymer matrix and thus has a considerableinfluence of the material end properties of the hardened polymer.Especially-affected thereby is the temperature stability which islimited by the salt of the amine remaining in the matrix. The basistherefor is the possibility of the acidolytic or aminolytic cleavage ofthe polydimethylsiloxane structure at elevated temperatures. Thus, forexample, already after some days continuous stressing at 250° C., anembrittlement is observed of a silicone mass accelerately hardened byaddition of oxalic acid dihydrate. Furthermore, by reaction of theoxalic acid with chalk at elevated temperatures, a gaseous decompositiontakes place.

Thus, the task forming the basis of the invention is to make available abuilding kit for the production of sealing and adhesive masses based onaminosilane-cross-linking polysiloxane mixtures, whereby these are toharden within a short time, i.e. within a few minutes up to severalhours and independently of the surrounding atmospheric moisture,whereby, besides the typical characteristics of the previously knownvulcanisates, such as, for example, inherent adhesion, mechanicalproperties and stability, especially the temperature stability of theaccelerately hardened silicone is to be improved.

It has now been found that the replacement of inorganic or organic acidsof the known constructional kits acting as accelerator components byacidic or basic neutral salts in the case of an accelerating action onthe hardening comparable with acids, provides a clearlyimproved-temperature stability of the silicones polymerised under theseconditions. By acidic or basic neutral salts are understood compounds inwhich calculatedly all ionisable hydrogen atoms of the acid are replacedby other cations and all OH groups of the cation base by acid anionsand, solely via the differing degree of dissociation of the underlyingacids and bases,the aqueous solutions of the salts react acidic orbasic, especially in the case of 1 molar solutions pH values of below 5or above 9, especially below 4 or above 10 are obtained. Furthermore, itwas found that, besides aminosilane, also oxime and alkoxy cross-linkerscan be advantageously used as components.

The task forming the basis of the invention is solved by the features ofthe main claim and promoted by those of the subsidiary claims. Suchconstructional kits for the production of the mixtures are characterisedin that they contain at least the following components:

A) 100 wt. parts of an at least bifunctionally terminateddiorganopolysiloxane, whereby this is built up from a linear or branchedchain of repeating units of the formula

 and—as shown in the following in the case of a linear chain—isterminated with functional end groups Z.

 There hereby mean:

R¹, R²: saturated or unsaturated hydrocarbon radicals with 1-15 carbonatoms, possibly substituted with halogen or cyano groups

Z: —H, —OH, —OR¹, —OSiR³(NR⁴R⁵)₂, —C—Si—(ON═CR⁴R⁵) ₃ and —C—Si—(OR³)₃

R³: hydrogen or monovalent saturated or unsaturated hydrocarbon orhydrocarbonoxy radical with 1-15 carbon atoms.

R⁴, R⁵: hydrogen and/or saturated or unsaturated aliphatic,cycloaliphatic or aromatic hydro-carbon radical with 1 to 15 carbonatoms, possibly substituted with halogen or cyano groups

B) 0.1 to 20 wt. parts of an aminosilane or oxime or alkoxy cross-linkerof the general formulae

R³ _(y)—Si—(NR⁴R⁵ )_(4−y),

R³ _(y)—Si—(ON═CR⁴R⁵)_(4−y)

R³ _(y)—Si—(OR³)_(4−y)

C) 0.1 to 20 wt. parts of a catalyst in the form of an acidic or basicneutral salt

D) 0 to 20 wt. parts water.

As example for the radicals R¹ and R² of the components A are to benamed any desired saturated alkyl radicals, such as methyl, ethyl,n-propyl, isopropyl, octyl, dodecyl, octadecyl, but also cyclic, such ascyclopentyl and cyclobexyl. Furthermore, there can be used unsaturatedaliphatic and cyclo-aliphatic radicals, such as vinyl, allyl,cyclo-pentenyl or cyclohexenyl and also aromatic, such as phenyl ornaphthyl, and aliphatic substituted radicals, such as for example benzylor toluyl. Within a poly-siloxane, the radicals R¹ and R² can be of thesame or also different construction. It is also possible to mix branchedand unbranched polysiloxanes with the above-described construction andin different chain length. Preferably, there are used polysiloxanesterminated with hydroxyl groups, so-called α,ω-dihydroxydiorganopolysiloxanes with methyl and phenyl radicals.

The said radicals can also be used in halogen- or cyano-substitutedform. Examples herefor are 1,1,1-trifluorotoluyl, β-cyancethyl or o-, m-or p-chlorophenyl radicals.

The viscosity of the diorganopolysiloxanes preferably lies in the rangeof 500 to 350000 mPas.

The radical R³ can, besides hydrogen, be of the same construction as theradicals R¹ and R². There are preferably used simple alkyl radicals,such as methyl or ethyl.

The radicals R⁴ and R⁵ can be of the same construction as the radicalsR¹, R² or R³, whereby one of the two radicals can also be hydrogen.Organoamino-silanes are preferably used which are obtained, for examplefrom reactions of methyltrichlorosilanes with primary, aliphatic orcycloaliphatic amines, especially with sec-butylamine orcyclohexylamine.

As component C are suitable acidic and basic neutral salts, such as forexample the acidic neutral salts of aluminium, especially the sulphate,the chloride and the nitrate, the aluminium alums of the ammonium ionand of the alkali metals, preferably of sodium and potassium.Furthermore, as advantageous representatives of the acidic neutralsalts, there are to be mentioned the salts of iron, thereby especiallyiron II sulphate, iron III phosphate,iron alum of the ammonium ion, aswell as ammonium iron II sulphate (Mohr's salt). Acceleratingly-actingbasic neutral salts are, for example, trisodium phosphate and sodiummetasilicate. The acidic or basic neutral salts can possibly also beused in combination.

Component D can be added to the mixture not only in liquid form but alsobound as water of crystallisation, for example as sodium sulphatedecahydrate, or enclosed in zeolites or also adsorbed on the surface offilling materials, such as for example calcium carbonate. The additionof component D preferably takes place in combination with component Cbound as water of crystallisation.

To the mixtures of the components A to D can be added further materialsfor the achievement of special properties. To be mentioned here areespecially coloured pigments and soluble coloured materials, stabilisersagainst oxidation and the action of beat, dispersants, reactioncatalysts, fungicides, adhesives, solvents, flame protection acents,plasticisers (preferably silicone oil-but also based on hydrocarbons),strengthening filling materials, such a for example highly dispersed orprecipitated silicic acids, granhite, carbon black, as well as passivefilling materials, such as e.g. calcium carbonate, silicates, quartzmeal, glass and carbon fibres, diatomaceous earth, metal powder, metaloxides, synthetic material powder, as well as hollow spheres of glass orsynthetic material. As silicic acids, there are preferably usedpyrogenic silicic acids, the polar surface of which is hydrophobed.

Mixtures of the components A to D are not storage-stable. Therefore, thecomponents C and D necessary for the reaction acceleration are admixedwith the mixture of the components A and B immediately before use in asuitable mould, preferably pasted in silicone oils or polymers of thecomponent A.

The present invention also concerns processes for the production of asealing or adhesive mixture or moulding mass based on at leastbifunctionally terminated diorganopolysiloxanes and cross-linkers whichare characterised in that

A) 100 wt. parts of such a diorganopolysiloxane, whereby this is builtup of a linear or branched chain of repeating units of the formula

 and, corresponding to the following on the special case of linearchains according to the formula

 is terminated with functional end groups Z, and whereby

R¹, R²: are saturated or unsaturated hydrocarbon radicals with 1-15carbon atoms, possibly substituted with halogen or cyano groups

Z: —H, —OH, —OR¹, —OSiR³(NR⁴R⁵)₂, —O—Si—(ON═CR⁴R⁵)₃ and —O—Si—(OR³)₃

R³: hydrogen or monovalent saturated or unsaturated hydrocarbon orhydrocarbonoxy radical

R⁴,R⁵: hydrogen and/or saturated or unsaturated aliphatic,cycloaliphatic or aromatic hydro-carbon radical with 1 to 15 carbonatoms, possibly substituted with halogen or cyano groups

B) 0.1 to 20 wt. parts of an aminosilane or oxime or alkoxy cross-linkerof the general formulae

R³ _(y)—Si—(NR⁴R⁵)_(4−y)

R³ _(y)—Si—(ON═CR⁴R⁵)_(4−y)

R³ _(y)—Si—(OR³)_(4−y)

whereby Y=0 or 1 and R³, R⁴ and R⁵ have the above meaning,

as well as possibly coloured pigments or soluble coloured materials,stabilisers against oxidation and the action of heat, dispersers,reaction catalysts, fungicides, adhesives, solvents, flame-protectionagents, plasticisers (preferably silicone oils but also plasticizersbased on hydrocarbons), furthermore, active, strengthening fillingmaterials, such as for example highly dispersed or precipitated silicicacids, graphite, carbon black, as well as passive filling materials,such as e.g. calcium carbonate, silicates, quartz meal, glass and carbonfibres, diatomaceous earth, metal powder, metal oxides, syntheticmaterial powder, as well as hollow spheres of glass or syntheticmaterial, are mixed with one another and immediately before use areadded

C) 0.1 to 20 wt. parts of a catalyst in the form of and acidic or basicneutral salt,

D) 0 to 20 wt. parts water, possibly pasted in silicone oils orpolymers.

The mixtures prepared with the help of the constructional kit accordingto the invention preferably harden at room temperature in 20 minutes to3 hours to give a solid, adhesion-free and cutable mass. Increasedtemperature in the case of the hardening (about 40° C.) brings about anadditional accelerating effect. The silicone mixtures adhere themselvesto substrates of glass, ceramic, wood, concrete, plaster, metals andsynthetic materials. A rapidly built up inherent adhesion is achievedespecially on glass, metals and synthetic materials with polar surface.Therefore, the mixtures according to the invention are advantageouslyused as adhesive or sealing materials, as protective coverings forelectrical insulation, as casting masses for electrical and electronicconstructional parts but also as moulding masses for the production ofimpressions or other moulded parts which are usefully produced fromelastomers.

In the following, the invention is explained in more detail on the basisof an Example.

EXAMPLE

100 wt. parts of a component I consisting of:

100 wt. parts of an α,ω-dihydroxydimethylpoly-siloxane with a viscosityof 20,000 mPa·s,

18 wt. parts of a highly dispersed silicic acid with a specific surfacearea according to BET of about 110 m²/g

15 wt. parts of a calcium carbonate filling material,

8 wt. parts tris-(cyclohexylamino)-methylsilane are homogeneously mixedtogether with 25 wt. parts of a component II consisting of:

100 wt. parts of an α,ω-dihydroxydimethylpolysiloxane with a viscosityof 20000 mPa·s,

9 wt. parts of a highly dispersed silicic acid with a specific surfacearea according to BET of about 150 m²/g,

2.5-3 wt. parts of an ammonium aluminium alum dodecahydrate of <100 μm.

The silicone mixture produced from the components of a constructionalkit according to the invention was hardened or mutable after about 25min at room temperature with exclusion of atmospheric moisture and,after one hour, achieved a Shore hardness of about 20-25. The endhardness, measured after 7 days, amounts to Shore A of about 40. Underthese conditions, both components remain storage-stable pastes. The massshows an astonishing temperature stability under temperature conditionsof up to 250° C. The weight loss in the case of a temperature stressingof 250° C. amounts, after one day, to about 5%, caused by emergingcleavage product, after 7 days to 8%. and, after 42 days, lies at about12%.

Furthermore, a rapidly built up inherent adhesion on various substrates,especially glass, metals and synthetic materials with polar surface, wasachieved. The initial adhesion on these substrates is thereby so strongalready after 30 min that a pulling off of the mass from the adhesionsurface is only possible with mechanical destruction. Adhered parts canalready be mechanically stressed after 30 minutes.

In the following Table, there are given further experiments with otheracidic or basic neutral salts, whereby the components I and II, as wellas the production , was carried out according to the above Example. Theamount of water introduced via the accelerator substance C therebyamount to about 0.3 g/100 g of I component, which suffices wholly orpreponderantly to hydrolyse the added cross-linker (B component). Aseparate addition of water (component D) is not necessary.

water of mixing crystall- pH ratio I:II hardened/ accelerator isationvalue (wt.parts) cutable acidic neutral salts: Al₂(SC₄)₃ 18 3-4100:25 >3 h NH₄Fe(SO₄)₂ 12 1 100:25 ˜60 min FePO₄ 4 100:25 ˜75 min FeSO₄7 3-4 100:25 ˜70 min NH₄Al(SO₄)₂ 12   3-4.5 100:25 ˜25 min AlCl₃ 62.5-3.5 100:25 ˜3 h KAl(SO₄)₂ 12   3-3.5 100:25 ˜60 min basic neutralsalts: Na₄P₂O₇ 10 8.8-9.4 100:25 ˜40 min Na₃PO₄ 10 12 100:25 ˜50 minNa₂SiO₃ 5 12.5 100:25 >3 h water addition (comparison) H₂O (Liquid) ˜2 dSiO₂ ⁺ × H₂O >>8 h

By the use of the acidic or basic neutral salts, systems based on oximeor alkoxy cross-linker can also be accelerated.

What is claimed is:
 1. Constructional kit for the production of rapidlyhardening, silicone masses of at least bifunctiorially terminateddiorganopolysiloxanes, cross-linkers, as well as optional fillingmaterials, additives and pigments, comprising the following components:A) 100 wt. parts of an at least bifunctionally terminateddiorganopolysiloxane, whereby this polysiloxane is built up from alinear or branched chain of repeating units of the formula

and contains at least two end groups Z with Z is one or more of: —H,—OH, —OR¹, —OSiR³ (NR⁴R⁵)₂ —O—Si—(ON═CR⁴R⁵)₃ or —O—Si—(OR³)₃ R¹, R²:saturated or unsaturated hydrocarbon radicals with 1 to 15 carbon atomsoptionally substituted with halogen or cyano groups, B) 0.1 to 20 wt.parts of a cross-linker, C) 0.1 to 20 wt. parts of an accelerator, D) 0to 20 wt. parts water, characterised in that the accelerator incomponent C is an acidic or basic neutral salt and the component B anaminosilane cross-linker of the general formula: R³_(y)—Si—(NR⁴R⁵)_(4−y)  whereby y=0 or 1, with R³: hydrogen or monovalentsaturated or unsaturated hydrocarbon or hydrocarbonoxy radical and R⁴,R⁵ are independently one or more of: hydrogen or saturated orunsaturated aliphatic, cycloaliphatic or aromatic hydrocarbon radicalwith 1 to 15 carbon atoms, optionally substituted with halogen or cyanogroups; or an oxime or alkoxy cross-linker of the general formula: R³_(y)—Si—(ONCR⁴R⁵)_(4−y) or R³ _(y—Si—(OR) ³)_(4−y)  whereby y=0 or 1 andR³, R⁴ and R⁵ have the above meaning.
 2. Constructional kit according toclaim 1, wherein the accelerator component C is contained in water ofcrystallisation-containing form.
 3. Constructional kit according toclaim 2, wherein as component D, water of crystallisation-hydratematerials or water absorbed on zeolites or silica gels or adsorbed infilling material surfaces is used.
 4. Constructional kit according toclaim 2, wherein there are additionally contained one or more ofcoloured pigments or soluble colouring materials, stabilisers againstoxidation and action of heat, dispersers, reaction catalysts,fungicides, adhesives, solvents, flame-protection agents, plasticisers,active, strengthening filling materials, or passive filling materials.5. Constructional kit according to claim 4, wherein the plasticiserscomprise one or more of silicone oils and plasticisers based onhydrocarbons; the active, strengthening filling materials comprise oneor more of highly dispersed or precipitated silicic acids, graphite orcarbon black; and the passive filling materials comprise one or more ofcalcium carbonate, silicates, quartz meal, glass or carbon fibres,diatomaceous earth, metal powder, metal oxides, synthetic materialpowder, or hollow spheres of glass or synthetic materials. 6.Constructional kit according to claim 2, wherein as diorganopolysiloxanecomponent A, there is used an α,ω-dihydroxydiorganopolysiloxane. 7.Constructional kit according to claim 1, wherein as component D, waterof crystallisation-hydrate materials or water absorbed on zeolites orsilica gels or adsorbed in filling material surfaces is used. 8.Constructional kit according to claim 7, wherein as diorganopolysiloxanecomponent A, there is used an α,ω-dihydroxydiorganopolysiloxane. 9.Constructional kit according to claim 7, wherein there are additionallycontained one or more of coloured pigments or soluble colouringmaterials, stabilisers against oxidation and action of heat, dispersers,reaction catalysts, fungicides, adhesives, solvents, flame-protectionagents, plasticisers, active, strengthening filling materials, orpassive filling materials.
 10. Constructional kit according to claim 9,wherein the plasticisers comprise one or more of silicone oils orplasticisers based on hydrocarbons; the active, strengthening fillingmaterials comprise one or more of highly dispersed or precipitatedsilicic acids, graphite or carbon black; and the passive fillingmaterials comprise one or more of calcium carbonate, silicates, quartzmeal, glass and carbon fibres, diatomaceous earth, metal powder, metaloxides, synthetic material powder, or hollow spheres of glass orsynthetic materials.
 11. Constructional kit according to claim 1,further comprising one or more of coloured pigments or soluble colouringmaterials, stabilisers against oxidation and action of heat, dispersers,reaction catalysts, fungicides, adhesives, solvents, flame-protectionagents, plasticisers, active, strengthening filling materials, orpassive filling materials, in the components A-D.
 12. Constructional kitaccording to claim 11, wherein the plasticisers comprise one or more ofsilicone oils or plasticisers based on hydrocarbons; the active,strengthening filling materials comprise one or more of highly dispersedor precipitated silicic acids, graphite or carbon black; and the passivefilling materials comprise one or more of calcium carbonate, silicates,quartz meal, glass or carbon fibres, diatomaceaous earth, metal powder,metal oxides, synthetic material powder, or hollow spheres of glass orsynthetic materials.
 13. Constructional kit according to claim 11,wherein as diorganopolysiloxane component A, there is used anα,ω-dihydroxydiorganopolysiloxane.
 14. Constructional kit according toclaim 1, wherein as diorganopolysiloxane component A, there is used anα,ω-dihydroxydiorganopolysiloxane.
 15. Process for the production of asealing or adhesive mixture based on diorganopolysiloxanes andaminosilane or oxime or alkoxy cross-linkers, wherein components A and Baccording to claim 1 are mixed to give a first pre-mixture and thecomponents C and D according to claim 1 to give a second pre-mixtureand, shortly before use, the two pre-mixtures are combined to give theeffective sealing and adhesive mixture.
 16. Process according to claim15, wherein component C comprises a compound which is contained in waterof crystallisation-containing form and component D comprises water ofcrystallisation-hydrate materials, water absorbed on zeolites or silicagels or adsorbed in filling material surfaces.
 17. Process according toclaim 16, wherein the components C and/or D, optionally in combinationwith materials selected from the group consisting of coloured pigmentsor soluble colouring materials, stabilisers against oxidation and actionof heat, dispersers, reaction catalysts, fungicides, adhesives,solvents, flame-protection agents, active, strengthening fillingmaterials, and passive filling materials, are pasted and a plasticiseris optionally added, which is based on silicone or thediorganopolysiloxane polymer.
 18. Process according to claim 16, whereinthe diorganopolysiloxane A is an α,ω-dihydroxydiorganopolysiloxane. 19.Process according to claim 15, wherein the components C and/or D,optionally in combination with materials comprising one or more ofcoloured pigments or soluble colouring materials, stabilisers againstoxidation and action of heat, dispersers, reaction catalysts,fungicides, adhesives, solvents, flame-protection agents, active,strengthening filling materials, or passive filling materials, arepasted, and a plasticiser is optionally added, which is based onsilicone or the diorganopolysiloxane polymer.
 20. Process according toclaim 19, wherein the diorganopolysiloxane A is anα,ω-dihydroxydiorganopolysiloxane.
 21. Process according to claim 19,wherein the plasticisers comprise one or more of silicone oils orplasticisers based on hydrocarbons; the active, strengthening fillingmaterials comprise one or more of highly dispersed or precipitatedsilicic acids, graphite or carbon black; and the passive fillingmaterials comprise one or more of calcium carbonate, silicates, quartzmeal, glass or carbon fibres, diatomaceous earth, metal powder, metaloxides, synthetic material powder, or hollow spheres of glass orsynthetic materials.
 22. Process according to claim 15, wherein thediorganopolysiloxane component A is anα,ω-dihydroxydiorganopolysiloxane.
 23. Process for sealing or bonding,comprising applying mixtures of the constructional kits according toclaim 1 to a surface to be sealed or bonded.
 24. Process for producing amolded mass, comprising molding mixtures of the constructional kitsaccording to claim 1 into a desired shape.